P3HT, SiC and ZnS based solar cells were investigated via SCAPS-1D to estimate the effect of different silicon carbide (SiC) polytypes as the interlayer, including 3C-SiC, 4H-SiC and 6H-SiC, on the device performance. Various analyses were performed to explain the charge transfer and interfacial behavior, including current-voltage (J-V), external quantum efficiency (EQE), Mott-Schottky and recombination rate. Among the solar cells studied, the use of 3C-SiC interlayer showed the highest performance and a clear reduction in interfacial recombination, achieving a short-circuit current density (JSC) of 15.18 mA cm2, a fill factor (FF) of 81.6% and a power conversion efficiency (PCE) of 19.2%. In contrast, 6H-SiC resulted in a modest improvement, while 4H-SiC resulted in a performance degradation. Further optimization of the 3C-SiC interlayer thickness, especially in the range of 70–100 nm, was crucial in balancing the band bending, interface passivation, and carrier extraction, factors that collectively contributed to maximizing the FF and PCE. Further investigations were conducted to study the effects of trap density, effective density of states, series and shunt resistances, and illumination conditions to assess their importance on solar cell performance. These findings indicate that the appropriate SiC polytype with precise interface engineering plays a crucial role in enhancing the efficiency of solar cells.
